The present invention relates to an electromagnetic valve for a high pressure fuel supply apparatus which, when supplying high pressure fuel from a fuel pump, is capable of controlling the flow rate of the high pressure fuel.
FIG. 6 is a block diagram of a fuel supply system in a vehicle internal combustion engine including a conventional electromagnetic valve for a high pressure fuel supply apparatus. In FIG. 6, fuel 2 stored in a fuel tank 1 is discharged from the fuel tank 1 by a low pressure pump 3 and passes through a filter 4; and, after the pressure of the fuel 2 is adjusted by a low pressure regulator 5, the fuel 2 is supplied to a high pressure fuel supply apparatus 6 which is a high pressure pump. While only the flow rate of the fuel 2 that is necessary for fuel injection is adjusted into high pressure fuel by the high pressure fuel supply apparatus 6, the fuel 2 is supplied into a delivery pipe 9 disposed in an internal combustion engine (not shown). The extra amount of the fuel 2 is relieved into between a low pressure damper 12 and a suction valve 13 by an electromagnetic valve 17.
Also, the necessary fuel rate is decided by a control unit (not shown) and the electromagnetic 17 is also controlled by the control unit. The thus supplied high pressure fuel is jetted out in the form of high pressure mist from fuel injection valves 10 connected to the delivery pipe 9 into the cylinders of the internal combustion engine. In case where the pressure of the interior of the delivery pipe 9 turns into an abnormal pressure (the pressure for opening a high pressure relief valve), a filter 7 and a high pressure relief valve 8 are respectively opened to thereby prevent the delivery pipe 9 against damage.
The high pressure fuel supply apparatus 6, which is a high pressure pump, includes a filter 11 for filtering the fuel supplied, a low pressure damper 12 for absorbing the pulsations of the low pressure fuel, and a high pressure fuel pump 16 which pressurizes the fuel supplied through the suction valve 13 to thereby jet out the high pressure fuel through a jet-out valve 14.
Now, FIG. 7 is a section view of a conventional high pressure fuel supply apparatus. In FIG. 7, the high pressure fuel supply apparatus 6 includes a casing 61, a high pressure fuel pump 16 consisting of a plunger pump disposed within the casing 61, an electromagnetic valve 17 and a low pressure damper 12, while these components are formed as an integrated unit.
In the high pressure pump 16, there are formed a sleeve 160, and a fuel pressurizing chamber 163 enclosed by a plunger 161 which is inserted into the high pressure pump 16 in such a manner that it is able to slide within the sleeve 160. The other end of the plunger 161 is contacted with a tappet 164; and, the tappet 164 is contacted with a cam 100 in order to be able to drive the high pressure fuel pump 16. The cam 100 is formed integrally or coaxially with the cam shaft 101 of the engine and can be operated in linking with the rotation of the crankshaft to move the plunger 161 reciprocatingly along the profile of the cam 100. The capacity of the fuel pressurizing chamber 163 varies according to the reciprocating motion of the plunger 161 and thus the fuel, which is pressurized into high pressure fuel, can be jetted out from the jet-out valve 14.
The high pressure fuel pump 16 is structured in the following manner: that is, a first plate 162, the suction valve 13, a second plate 166 and the flange portion of the sleeve 160 are held by and between the casing 61 and the end face of a spring guide 165 as well as are fastened by a bolt 180. The first plate 162 includes a fuel suction port 162a for sucking the fuel from the low pressure damper 12 into the fuel pressurizing chamber 163, and a fuel jet-out port 162b for jetting out the fuel from the fuel pressurizing chamber 163.
The suction valve 13, which has a thin-plate shape, is held by and between the first and second plates 162 and 166, while a valve body of the suction valve 13 is disposed in the fuel suction port 162a. The jet-out valve 14 is disposed on the top portion of the fuel jet-out port 162b and is allowed to communicate with the delivery pipe 9 through a high pressure fuel jet-out passage 62 formed within the casing 61. Also, for suction of the fuel, there is interposed a spring 167 for pressing down the plunger 161 in a direction to expand the fuel pressurizing chamber 163 in such a manner that the spring 167 is compressed between the spring guide 165 and a spring holder 168.
Now, FIG. 8A is a section view of the conventional electromagnetic valve for a high pressure fuel supply apparatus; and, FIG. 8B shows section views respectively taken along the lines Axe2x80x94A, Bxe2x80x94B and Cxe2x80x94C shown in FIG. 8A. Also, FIG. 9 shows enlarged section views of the contact portion between a valve member and a valve seat. In FIGS. 8A and 8B, the electromagnetic valve 17 includes an electromagnetic valve main body 170 incorporated into the casing 61 of the high pressure fuel supply apparatus 6 and including a fuel passage 172 therein, a valve seat 173 disposed within the fuel passage 172 of the electromagnetic valve main body 170, a hollow cylindrical-shaped valve member 174 detachable from and contactable with the valve seat 173 within the electromagnetic valve main body 170 to thereby open and close the fuel passage 172, and a compression spring 175 for pressing the valve member 174 against the valve seat 173. The terminal 176 of a solenoid coil 171 is guided to a connector 178 and is connected to an external circuit (not shown).
In the jet-out stroke of the high pressure fuel pump 16, at the time when the flow rate required by the control unit (not shown) is jetted out, the solenoid coil 171 wound around the periphery of a core 177 fixedly secured to the electromagnetic valve main body 170 of the electromagnetic valve 17 is excited and, due to the thus-excited electromagnetic force, the valve member 174 is detached from the valve seat 173 against the operation force of the compression spring 175 and is thereby opened.
The fuel, as shown by arrow marks in FIG. 9, moves from the fuel passage 172, passes through a clearance between the valve seat 173 and valve member 174, and flows into an oil passage 174a which is a hollow portion of the valve member 174. The fuel, which has flown into the oil passage 174a, moves through cut-out oil passages 174b respectively formed in the outer peripheral portion of the valve member 174 as well as through a diameter-direction oil passage 181a formed in a stopper 181, and is then relieved to the low pressure side.
As described above, by relieving the fuel 2 within the fuel pressurizing chamber 163 to the low pressure side between the low pressure damper 12 and suction valve 13, the pressure of the interior of the fuel pressurizing chamber 163 is reduced down to the pressure of the delivery pipe 9 or lower, thereby closing the jet-out valve 14. After then, the valve member 174 of the electromagnetic valve 17 remains open until the high pressure fuel pump 16 moves to the suction stroke. By controlling the valve opening timing of the electromagnetic valve 17, the quantity of the fuel to be jetted-out to the delivery pipe 9 can be adjusted.
However, in the conventional high pressure fuel supply apparatus, as shown in FIG. 9, since the valve seat 173 and valve member 174 are contacted with each other in a flat shape, when the valve member 174 is opened, the flow of the fuel in the periphery of the valve member 174 turns from sudden reduction to sudden expansion, the fuel flow detaches from the wall surface of the valve member 174 on the downstream side to thereby cause a backward flow (eddy) and thus narrow the oil passage, which results in the large fuel pressure loss.
Also, as shown in FIG. 10, when the valve seat 173 and valve member 174 are contacted with each other in their respective taper portions, since the seat portion of the valve member 174 is formed in a taper shape, the valve member 174 is properly centered to thereby be able to control an ill influence, that is, the fuel leakage of the valve that could otherwise be caused by working variations in the valve member 174; however, when the valve member 174 is opened, the fuel flow in the periphery of the valve member 174 turns from sudden reduction to sudden expansion, the fuel flow detaches from the wall surface of the valve member 174 on the downstream side to thereby cause a backward flow (eddy) and thus narrow the oil passage. Therefore, although not so large as in the case shown in FIG. 9, there is caused a large fuel pressure loss.
Also, due to the above-mentioned fuel pressure loss in the vicinity of the seat portion, the fuel flow near the seat portion becomes unstable, thereby causing cavitations in the interior of the electromagnetic valve 17, which gives rise to the eroded electromagnetic valve 17.
The present invention aims at eliminating the above-mentioned drawbacks found in the conventional electromagnetic valve for a high pressure fuel supply apparatus. Accordingly, it is an object of the invention to provide an electromagnetic valve for a high pressure fuel supply apparatus which can control the fuel pressure loss in the vicinity of the seat portion of the valve member to thereby be able to prevent the occurrence of cavitations in the interior of the electromagnetic valve and thus prevent the interior of the electromagnetic valve against erosion.
In attaining the above object, according to the invention, there is provided an electromagnetic valve for a high pressure fuel supply apparatus constituted by: an electromagnetic valve main body including a fuel passage to be connected between the high and low pressure sides of the fuel supply apparatus; a valve seat disposed in the fuel passage; a valve member disposed within the electromagnetic valve main body in such a manner that it can be detached from and contacted with the valve seat to thereby open and close the fuel passage; and, a solenoid coil for moving the valve member with respect to the valve seat, whereby the jet-out quantity of the fuel from the high pressure fuel supply apparatus can be maintained at a given value, characterized in that the valve seat includes an inclined surface having a given angle with respect to the moving direction of the valve member and the valve member has an R shape in the portion thereof which, when the valve member is closed, can be contacted with the inclined surface of the valve seat.
Also, the valve member is a valve of a normally closed type that it is closed when the solenoid coil is in a non-electrically conduct state.